I am in the middle of replacing the original exhaust on my 88 convertible with a racing beat true dual setup. Since I bought it second hand, I don't have the instructions and I can't find them on their website.

Does anyone know what happens to the 2 hoses that went to the split air pipe?

 

Hardpipes? From Airpump?

haven't had any emissions crap for sometime, so I can only speculate.

 

The 2 hoses went to a metal pipe that feed into the cat. Since the true dual system doesn't have a cat, I am not sure what to do with these two hoses. If you have the FSM, it is on page 4A-4. The larger of the 2 hoses is labeled "B" in the diagram.

 

The split air is also used to open your 5/6 ports so you will want to connect it.

 

*the small tube opens the 5/6th ports, and the big one was meant to inject some air into the cat to help it work efficiently.

If you have the S4 version of the true dual exhaust there should be a little pickup tube on the header you can attach the little tube to.. Otherwise do a search for other ways to activate the 5/6th ports [air pump or electronic]

 

If there's not a small pipe on the header then you need to buy the right header or add a small pipe/port to it so you can run a hose up to the hard pipe for the 6pi diaphrams. Or add an electric air pump controlled by rpm. like a msd rpm switch and relay. Easiest for your car to just run a hose to the exhaust. The split air pipe gets deleted. The true dual exhaust is for racing. This means the air pump and acv go away as well as they no longer serve a purpose. As long as you leave the split air solenoid and the (CAn't remember right now) other solenoid plugged in on the harness the ecu will think they are still there and operational. I know you don't have a check engine light to worry about but there are ways to retrieve the codes and it would be better to not have any set so when you check them you don't have to count them all the time. You probably have a S5 header.

I have the same exhaust and it has no pipe either for the 6pi. The s5 doesnt use that method anyways but just to let you know. A muffler shop could add a small pipe to that header for probably $10

BTW that exhaust system sounds badass!

 

I called Racing Beat and the exhaust has an optional block off plate for the ACV. I'm guessing that plate is still on the car I took the exhaust off of and it is too much of a hassle to go back and get it. So I bought a new one for 10-15 bucks.

When they sent it to me, it included a small hose to go to the 5th and 6th ports. I spent yesterday afternoon installing and removing the ACV and air pump. Now I just need to finish putting the rest of the small parts back on the car so I can take it out for a road test.

The only remaining question I have is about the large hose that fed the split air pipe going to the old cat. Does it need to be capped off?

 

if you're pulling the ACV then you should remove the split air pipe and block it off with a blockoff plate. The split air pipe is useless without an ACV and airpump.

 

True dual exhaust? Doesn't that require 2 manifolds is essance? Otherwise its always going to split off the 1 manifold.

 

I dont even know if the pressure from one runner will be enough to activate the 5/6th ports.
I have the true duals but I have the S5 headers, not the S4, I wired my 5/6th ports to open all the time anyways because damn thing is stuck lol, dont feel like fixing it. Havent had any low end problem for almost 3 years

 

You are correct. The ACV did come off and a block off plate was used. The split air pipe was also removed. However it has 2 hoses attached to it. The smaller is used to back feed from the Racing Beat header to open the 5th/6th ports.

 

The true dual header is setup so that each rotar's output goes into its own pipe. The pipes are completely independant all the way back. Here is a link to it:

http://www.racingbeat.com/RX7-1986-1...ems/16128.html

 

I sent an email to Jim Tanner with Racing Beat this morning about the extra hose. I'll post the reply when I get it. For now, i just left the hose disconnected. I'm planning on taking the car out later this week, so I guess I find out right away if that is going to cause a problem.

I had heard of people wiring the ports open and wondered if it had any negative effects.

 

i have a 88 vert also and used the same set up (racing beat true duels) with a s5 header.
i had removed the acv and blocked it off, but i only remember 2 houses, one BIG one SMALL.
big one goes to acv, the small one goes to 5th and 6th port actuators,or the small hard line located on the lower intake manifold witch your suppost to use.
i had ordered the exact pipe used off the s4 road race header from RB, and had a local shop weld in right where racing beat puts it on their s4 road racing(true duel) headers. you only need like 6psi to open the 5th & 6th ports.

basically all you need is the block off plate for the acv, and the pick up tube off the header for the 5th and 6th ports.

 

Here are some pics of the hose and where it attached to the split air pipe.



This is the hose coming off of the back of the engine. It is between the two hard lines.



Here is the point on the split air pipe it was connected.

I took the car out last night and the original issue I was having with it running on one rotor is fixed. I am hoping it was just a clogged cat.

It does have a new problem. It is suffering from the 3800 RPM hesitation, which it never did before. I plan to go over the grounds this weekend, but I would like to be sure this hose not being attached to something or blocked off is not a cause or contributing to the problem.